I have never heard of cleansing a deck with aromatherapy oil! This is new to me. I would be very careful because they are pure oil and some are even dark in colour.
You could always burn the oil in a burner and hold the deck over the steam I suppose. Incense would be better for cleansing a deck. If you do go for oils though - I would go with something like lavender or sandlewood - make sure it's a smell that you like!
Is it to get rid of or disguise a smell? maybe a smoker had the deck before you?